This invention relates to the sintering of metal powders into structures without the use of sintering aids. Metal powders, in particular aluminum and iron powders, have been difficult to sinter into porous structures due to the oxidation of the metals into their more highly oxidized states.
In U.S. Pat. No. 4,758,272 ('272) to be issued July 19, 1988 (on application Ser. No. 07/054,845), which is herein incorporated by reference, sintering of aluminum-iron alloys are disclosed. In the '272 patent the presence of a small amount of sintering aid was found necessary, such as an alkaline earth metal, to act as a getter for oxygen. Aluminum-iron alloys in the presence of oxygen forms a durable aluminum oxide layer and a not so durable iron oxide layer which inhibits the sintering of the metal powder into a hard porous body.
The present invention solves the sintering problems associated with aluminum powder and/or its iron powder alloy, and the subsequent oxide formations that may form in these bodies under sintering conditions. It has been found by sintering in a controlled atmosphere that aluminum powder and/or its iron powder alloys may produce hard porous bodies that do not require a sintering aid.